Attachment of composite lug to composite structural tube

ABSTRACT

The present disclosure describes lug clusters for composite tubes and methods for making such lug clusters. Lug clusters of the present disclosure may include a first side, a second side, and a saddle. The saddle may be placed in adjacent contact with a tube and a filament may be wound around the lug cluster and tube. The wound lug cluster and tube may be resin transfer molded. Machining may follow to remove material and finalize the shape of the lug cluster and/or tube. Thus, a lug cluster may be attached to a composite tube.

FIELD

The present disclosure relates generally to lug clusters and morespecifically to lug clusters for use with composite tubes.

BACKGROUND

Various types of aircraft utilize tubes such as struts including, forexample, to deploy nose, body, and/or wheel landing gear systems.Conventionally, aircraft landing gear include metal tubes and structuralcomponents, for example, landing gear strut tubes. Such components aremade of metallic materials and often comprise complex geometries andhigh strengths. However, these metallic components are typically heavy.

SUMMARY

A lug cluster is disclosed in accordance with various embodiments. Thelug cluster may include a first side having a flange including a firstside groove receiving a fiber filament according to a filament path, asecond side having a flange including a second side groove receiving thefiber filament according to the filament path, and a saddle. The saddlemay include a floor member having a planar member formed to follow acontour of a composite tube and an upper infill member resting on thefloor member and positioned between the first side and the second side.

A method of manufacturing a lug cluster is disclosed in accordance withvarious embodiments. The method may include forming a first side havinga first side including a flange with a first side groove and forming asecond side having a flange with a second side groove. The first sideand second side are joined together by a saddle having a floor memberincluding a planar member shaped to follow a contour of a compositetube. The method may include wrapping a first filament along a filamentpath disposed along the first side groove and the second side groove,whereby the lug cluster is secured in compression against the compositetube. The method may further include consolidating the composite tubeand the lug cluster by resin transfer molding and forming an upperinfill member resting on the floor member and positioned between thefirst side and the second side. A wrap of fiber, such as a continuouswrap of fiber around the lug and tube secures the lug to the tube andreacts loads that may otherwise pull the lug from the tube.

A landing gear system is disclosed in accordance with variousembodiments. The landing gear system may include a composite tube, afirst lug cluster mounted to the composite tube, and a second lugcluster mounted to the composite tube. The composite tube may compriseat least one of a filament wound composite tube, a filament braidedtube, and a composite tube of laid up filament. In various embodiments,the first lug cluster and the second lug cluster are oriented at anangle to one another.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosure, however, may bestbe obtained by referring to the detailed description and claims whenconsidered in connection with the drawing figures, wherein like numeralsdenote like elements.

FIGS. 1 illustrates a composite structural tube having various lugclusters, in accordance with various embodiments;

FIGS. 2A-B illustrate lug clusters in the process of being joined to acomposite structural tube, in accordance with various embodiments;

FIG. 2C illustrates a lug cluster aligned in a co-axial orientation andin the process of being joined to a composite structural tube, inaccordance with various embodiments;

FIGS. 3A-B illustrate various views of a lug cluster according to FIG.2A;

FIGS. 3C-D illustrate various views of a lug cluster according to FIG.2B;

FIGS. 3E-H illustrate various views of various lug clusters according toFIG. 2C;

FIG. 4A illustrates a lug cluster finally joined to a composite tube, inaccordance with various embodiments;

FIGS. 4B-C illustrate lug clusters aligned in a co-axial orientationfinally joined to a composite tube, in accordance with variousembodiments;

FIGS. 5A-F illustrate various shear features of a lug cluster and atube, in accordance with various embodiments; and

FIG. 6 depicts a method of forming a lug cluster, in accordance withvarious embodiments.

DETAILED DESCRIPTION

The detailed description of exemplary embodiments herein makes referenceto the accompanying drawings, which show exemplary embodiments by way ofillustration and their best mode. While these exemplary embodiments aredescribed in sufficient detail to enable those skilled in the art topractice the inventions, it should be understood that other embodimentsmay be realized and that logical and mechanical changes may be madewithout departing from the spirit and scope of the inventions. Thus, thedetailed description herein is presented for purposes of illustrationonly and not for limitation. For example, any reference to singularincludes plural embodiments, and any reference to more than onecomponent or step may include a singular embodiment or step. Also, anyreference to attached, fixed, connected or the like may includepermanent, removable, temporary, partial, full and/or any other possibleattachment option.

The present disclosure describes lug clusters for use with compositestructural tubes.

Such lug clusters may be used in aircraft systems, such as, for example,landing gear systems. However, the systems and methods of the presentdisclosure may be suitable for use in non-aircraft systems as well.

Aircraft landing gear increasingly implement composite features, such ascomposite strut tubes. While metal strut tubes are typically resilientunder side loading, composite strut tubes may implement attached lugclusters whereby side load may be conducted into various supportingstructures, rather than through the composite strut tube. Moreover,composite tubes may be used in actuator systems. Various lug clustersmay be attached whereby an actuation force exerted by an actuator may beconducted to various structures that are desired to be actuated.

A landing gear system may comprise a tube and a lug cluster. Withreference to

FIG. 1, landing gear system 100 in accordance with various embodimentsmay comprise multiple lug clusters 1-1, 1-2, and 1-3 attached atdifferent points to the tube 2. Various lug clusters 1-1, 1-2, and 1-3may have various orientations, for instance, lug clusters 1-1 and/or 1-3are oriented in a different direction than lug cluster 1-2. Various lugclusters 1-1, 1-2, and 1-3 may attach to the tube 2 at various locationsand may extend between the tube 2 and other aircraft structures. Thetube 2 may comprise a composite tube. For example, the tube 2 maycomprise a filament wound composite tube, a filament braided tube, acomposite tube of laid up filament and/or a combination thereof. Forexample, the composite tube may comprise carbon fiber and/or ceramicmaterials and/or fiberglass. The composite tube may comprisepolyacrylonitrile fibers such as oxidized polyacrylonitrile fibers orcarbonized polyacrylonitrile fibers. The composite tube may comprisefibrous structures infiltrated with a thermosetting and/or thermoplasticmaterial and/or resin. The composite tube may comprise lightweightpolymer matrix composite such as a carbon fiber composite material or ahydrocarbon fiber composite material. Thus, a landing gear system 100may comprise a tube 2, first lug cluster 1-1, and a second lug cluster1-2. The first lug cluster 1-1 and the second lug cluster 1-2 may havedifferent orientations, for instance, oriented at an angle to oneanother, such as a right angle, or any other angle.

Although composite materials provide reduced weight over traditionalmetal components, it may be difficult to couple composite materials tometal components. Conventional methods of attaching composite materialsto other materials, such as threading or drilling holes in the compositematerial, may significantly reduce the strength of the compositematerial. Joining composite materials with metallic components oftenpresents challenges due to different material characteristics. Joiningcomposite materials with to other composite materials also may presentchallenges. In that regard, it may not be suitable to couple a metalliclug cluster to a composite tube using traditional methodologies. Asdescribed herein, a fibrous member may be used to load a lug cluster 1in compression with a composite tube 2. Thus, the fibrous member maycouple the lug cluster 1 to the tube in a manner in which the lugcluster 1 is able to bear a load in any direction.

With reference to FIGS. 2A, 2B, 3A, 3B, 3C, and 3D, a lug cluster 1 maycomprise a first side 3 a, a second side 4 a and a saddle 5 a. Thesaddle 5 a may rest in surface-to-surface contact against the outersurface of the tube 2 forming a cylinder section with a profile lying inthe X-Y plane and an axis extending in the Z-direction. The first side 3a and the second side 4 a may be disposed at opposite ends of the saddle5 a along the X-axis and may extend outwardly from the saddle 5 a alongY-axis and lying in the Y-Z plane. In various embodiments, the firstside 3 a and the second side 4 a extend along parallel tangents of thesurface of the tube 2.

With reference to FIGS. 2C, 3E, and 3F, a lug cluster 1 may comprise afirst side 3 b, a second side 4 b and a saddle 5 b. The saddle 5 b mayrest in surface-to-surface contact against the outer surface of the tube2 forming a cylinder section with a profile lying in the X-Y plane andan axis extending in the Z-direction. The first side 3 b and the secondside 4 b may be disposed at opposite ends of the saddle 5 b along theZ-axis and may extend outwardly from the saddle 5 b along Y-axis andlying in the X-Y plane.

With reference to FIGS. 3G-H, a lug cluster 1 may comprise a first side3 c, a second side 4 c and a saddle 5 c. The saddle 5 c may rest insurface-to-surface contact against the outer surface of the tube 2forming a cylinder section with a profile lying in the X-Y plane and anaxis extending in the Z-direction. The first side 3 c and the secondside 4 c may be disposed at opposite ends of the saddle 5 c along theZ-axis and may extend outwardly from the saddle 5 c along Y-axis andlying in the X-Y plane. In various embodiments, the first side 3 c andthe second side 4 c extend away from the surface of the tube 2 at arelative angle to the surface of the tube.

With reference to FIGS. 2-3H, the first side 3 a, 3 b, 3 c and thesecond side 4 a, 4 b, 4 c may each have a shape, such as being generallytriangular with a radiused vertex, or trapezoidal, or rectangular, orany shape as desired. In various embodiments, the first side 3 a, 3 b, 3c and the second side 4 a, 4 b, 4 c have the same shape, while infurther embodiments, the first side 3 a, 3 b, 3 c and the second side 4a, 4 b, 4 c have different shapes, such as, for example, to maintainappropriate clearance from surrounding structures. With reference toFIGS. 3G-H, the first side 3 c and the second side 4 c may be swept atan angle so as not to extend perpendicularly to the axis of the tube 2,but to extend at an angle to the axis of the tube 2. The first side 3 cmay extend a greater distance outwardly relative to the tube than thesecond side 4 c.

With reference to FIGS. 2-3H, first side groove 6 a or first side groove6 b may comprise a channel disposed in the outer periphery of the firstside 3 a, 3 b, 3 c. With reference to FIGS. 2A, 2C, 3A-B, and 3E-H, thefirst side groove 6 a may penetrate into the first side 3 a, 3 b, 3 c,outwardly bounded by a portion of the first side. With reference toFIGS. 2B, and 3C-D, the first side groove 6 b may comprise a helicalportion. The helical portion may comprise a portion wherein thepenetration into the first side 3 a, 3 b, 3 c shifts from one face ofthe first side 3 a, 3 b, 3 c to another face of the first side 3 a, 3 b,3 c, so that a part of the helical portion is not outwardly bounded bythe first side 3 a, 3 b, 3 c, but rather extends into the first side 3a, 3 b, 3 c according to a helical path. Thus, the helical portion mayfollow the outer periphery of the first side 3 a, 3 b, 3 c, but may alsoat least partially extend through the outer periphery of the first side3 a, 3 b, 3 c. The channel may have an arcuate profile. In furtherembodiments, the channel may have a trapezoidal profile, or a triangularprofile, or may comprise any profile as desired.

Similarly, with reference to FIGS. 2-3H, second side groove 9 a orsecond side groove 9 b may comprise a channel disposed in the outerperiphery of the second side 4 a, 4 b, 4 c. With reference to FIGS. 2A,2C, 3A-B, and 3E-H, the second side groove 9 a may penetrate into thesecond side 4 a, 4 b, 4 c, outwardly bounded by a portion of the secondside. With reference to FIGS. 2B, and 3C-D, the second side groove 9 bmay comprise a helical portion. The helical portion may comprise aportion wherein the penetration into the second side 4 a, 4 b, 4 cshifts from one face of the second side 4 a, 4 b, 4 c to another face ofthe second side 4 a, 4 b, 4 c, so that a part of the helical portion isnot outwardly bounded by the second side 4 a, 4 b, 4 c, but ratherextends into the second side 4 according to a helical path. Thus, thehelical portion may follow the outer periphery of the second side 4 a, 4b, 4 c, but may also at least partially extend through the outerperiphery of the second side 4 a, 4 b, 4 c. The channel may have anarcuate profile. In further embodiments, the channel may have atrapezoidal profile, or a triangular profile, or may comprise anyprofile as desired.

With reference to FIGS. 2A-3H, the first side may comprise a first sidegroove 6 a, 6 b and the second side may comprise a second side groove 9a, 9 b. A fiber filament may be wrapped around the first side groove 6a, 6 b and the second side groove 9 a, 9 b according to a filament path20 a, 20 b. The fiber filament may be an individual strand of fiber, ormay be a series of strands of fiber on a flat tape, or any filament asdesired. The fiber filament may be a continuous fiber, or may bediscontinuous fibers. A fiber filament may be wrapped along first sidegroove 6 a, 6 b, around the tube 2, through second side groove 9 a, 9 b,around the tube 2, and back to the first side groove 6 a, 6 b. The fiberfilament may be wrapped in other direction, and/or wraps may cross underthe tube 2. While in various embodiments, a continuous fiber is wrappedalong the first side groove 6 a, 6 b and second side groove 9 a, 9 b, infurther embodiments (such as with reference to FIG. 2C illustrating afilament path 20 b) separate fibers are wrapped along the first sidegroove than are wrapped along the second side groove.

With reference to FIGS. 1-4C, saddle 5 a, 5 b, 5 c may comprise floormember 13. Floor member 13 may comprise a generally planar member thatis formed to follow a contour of the tube 2. For instance, floor member13 may have a profile corresponding to a partial circumference of thetube 2. Floor member 13 may be disposed between the first side 3 a, 3 b,3 c and the second side 4 a, 4 b, 4 c and may join the first side 3 a, 3b, 3 c and the second side 4 a, 4 b, 4 c. In various embodiments, thefloor member 13 comprises a tube contour edge 14 (e.g., see FIG. 3A). Atube contour edge 14 may comprise an arc configured to follow the arc ofa surface of the tube 2. In various embodiments, the floor member 13 hasa profile corresponding to a partial circumference of the tube 2 that isless than ½ of the circumference of the tube 2. In various embodiments,the floor member 13 has a profile corresponding to a partialcircumference of the tube 2 that is equal to ½ of the circumference ofthe tube 2. In various embodiments, the floor member 13 has a profilecorresponding to a partial circumference of the tube 2 that is >than ½of the circumference of the tube 2. In various embodiments, the floormember 13 has a profile corresponding to a partial circumference of thetube 2 that is <=½ of the circumference of the tube 2 or that is >=½ ofthe circumference of the tube 2. A tube contour edge 14 may beimplemented to assist the floor member 13 in laying smoothly insurface-to-surface contact to the tube 2, such as without buckling,wrinkling, and/or the like. Thus, the tube contour edge 14 may comprisea circle section having a radius equal to the radius of the tube 2.

With reference to FIGS. 5A-F, in various embodiments, the lug 1 and thetube 2 may comprise corresponding shear features. For instance, a shearfeature may be formed in the lug 1 at the interface of the lug 1 to thetube 2 corresponding to a conjugate shear feature formed in the tube 2at the interface of the lug 1 to the tube 2. Shear features may comprisetongues and grooves, keys and keyways, abutting ribs, and/or the like.For instance, with reference to FIG. 5A, a shear feature comprising acircumferential tongue 31 is formed in the tube 2 at the interface ofthe lug 1 to the tube 2 corresponding to a conjugate shear featurecomprising a circumferential groove 32 formed in the lug 1 at theinterface of the lug 1 to the tube 2. With reference to FIG. 5B, a shearfeature comprising an axial tongue 33 is formed in the tube 2 at theinterface of the lug 1 to the tube 2 corresponding to a conjugate shearfeature comprising an axial groove 34 formed in the lug 1 at theinterface of the lug 1 to the tube 2. With reference to FIG. 5C, a shearfeature comprising an crossed tongue 35 is formed in the tube 2 at theinterface of the lug 1 to the tube 2 corresponding to a conjugate shearfeature comprising an crossed groove 36 formed in the lug 1 at theinterface of the lug 1 to the tube 2. With reference to FIG. 5D, a shearfeature comprising an aligned circumferential groove set 37 is formed inthe tube 2 at the interface of the lug 1 to the tube 2 corresponding toa conjugate shear feature comprising an aligned circumferential grooveset 38 formed in the lug 1 at the interface of the lug 1 to the tube 2.With reference to FIG. 5E, a shear feature comprising an aligned axialtongue set 39 is formed in the tube 2 at the interface of the lug 1 tothe tube 2 corresponding to a conjugate shear feature comprising analigned axial groove set 40 formed in the lug 1 at the interface of thelug 1 to the tube 2. With reference to FIG. 5F, a shear featurecomprising an closed trapezoidal tongue 41 is formed in the tube 2 atthe interface of the lug 1 to the tube 2 corresponding to a conjugateshear feature comprising a closed trapezoidal axial groove 42 formed inthe lug 1 at the interface of the lug 1 to the tube 2. The shearfeatures may be oriented to ameliorate a tendency of the completed lug 1to twist around the tube (FIG. 5B, 5C, 5E, 5F) and/or may be oriented toameliorate a tendency of the completed lug 1 to translate along thelength of the tube (FIG. 5A, 5C, 5D, 5F). Moreover, in variousembodiments, shear features may be introduced to the tube 2 alone, suchas to restrain the freedom of the lug 1 to move about the tube 2. Forinstance, shear features may abut one or more side of the lug 1. In thismanner, the integrity of the bond, such as between the lug 1 and tube 2,such as created by resin, may be enhanced. Moreover, shear featuresand/or other surface features may be included to assist in orientationand alignment of the lug 1 and the tube 2 during assembly, and/or keyingof specific lugs 1 to specific sites on the tube 2. In variousembodiments, the shear features are formed directly in the lug and/ortube. In further embodiments, the shear features are produced byaddition of a shell to the lug 1 and/or tube 2.

With reference to FIGS. 4A-C, the saddle 5 a, 5 b, 5 c may furthercomprise an upper infill member 12. An upper infill member 12 maycomprise a first material composition forming a boss extending in theY-axis direction away from the floor member 13 and positioned betweenthe first side 3 a, 3 b, 3 c and the second side 4 a, 4 b, 4 c relativeto the X-Z plane (FIG. 4A) or relative to the X-Y plane (FIGS. 4B-C).The upper infill member 12 may be bounded by the projected edge of atleast one of the first side 3 a, 3 b, 3 c and the second side 4 a, 4 b,4 c, and may extend away from the floor member 13 in the Y-axisdirection, forming an integral boss.

The first side 3 a, 3 b, 3 c may further comprise a first sideattachment point 7. A first side attachment point 7 may be configured toreceive a structure desired to be attached to the tube 2 via the lugcluster 1. For instance, a first side attachment point 7 may comprise anaperture formed through and defined by (i.e., bounded by) the first side3 a, 3 b, 3 c. The aperture may be positioned above the upper infillmember 12 (e.g., relatively farther away along the Y-axis relative tothe floor member 13). The aperture may be oriented in alignment (e.g.,co-axial centers) corresponding with a second side attachment point 10of the second side 4 a, 4 b, 4 c. The first side attachment point 7 mayfurther comprise a bushing, such as a metallic bushing, a non-metallicbushing, and/or a self-lubricating element.

The second side 4 a, 4 b, 4 c may further comprise a second sideattachment point 10. A second side attachment point 10 may be configuredto receive a structure desired to be attached to the tube 2 via the lugcluster 1. For instance, a second side attachment point 10 may comprisean aperture formed through and defined by the second side 4 a, 4 b, 4 c.The aperture may be positioned above the upper infill member 12 (e.g.,relatively farther away along the Y-axis relative to the floor member13). The aperture may be oriented in alignment corresponding with afirst side attachment point 7 of the first side 3 a, 3 b, 3 c. Thesecond side attachment point 10 may further comprise a bushing, such asa metallic bushing, a non-metallic bushing, and/or a self-lubricatingelement. With reference to FIG. 4A, the first side attachment point 7and the second side attachment point 10 may align coaxially, with ashared axis oriented perpendicular to the axis of the tube 2 with whichthe lug cluster 1 is associated. With reference to FIG. 4B, the firstside attachment point 7 and the second side attachment point 10 mayalign coaxially, with a shared axis oriented parallel to the axis of thetube 2 with which the lug cluster 1 is associated. With reference toFIG. 4C, the first side attachment point 7 and the second sideattachment point 10 may align coaxially, with a shared axis oriented atan acute angle having at least a partially parallel vector component tothe axis of the tube 2 with which the lug cluster 1 is associated. Infurther embodiments, the first side attachment point 7 and the secondside attachment point 10 may align coaxially, with a shared axisoriented at an obtuse angle having at least a partially parallel vectorcomponent to the axis of the tube 2 with which the lug cluster 1 isassociated, or any angle as desired.

With reference to FIGS. 4A-B, the first side 3 a, 3 b, 3 c may furthercomprise a first side lightening pocket 8. A first side lighteningpocket 8 may comprise an aperture formed through and defined by thefirst side 3 a, 3 b, 3 c. The first side lightening pocket 8 maycomprise material removed from the first side 3 a, 3 b, 3 c generallyaligned with the upper infill member 12.

The second side 4 a, 4 b, 4 c may further comprise a second sidelightening pocket 11.

A second side lightening pocket 11 may comprise an aperture formedthrough and defined by the second side 4 a, 4 b, 4 c. The second sidelightening pocket 11 may comprise material removed from the second side4 a, 4 b, 4 c generally aligned with the upper infill member 12.

Having described various structural aspects of a lug cluster 1, methodsof making a lug cluster 1 are now disclosed. For instance, the saddle 5a, 5 b, 5 c may be manufactured. The saddle 5 a, 5 b, 5 c may be used asa tool during subsequent manufacturing steps as well as a structuralaspect of the lug cluster 1. The saddle 5 a, 5 b, 5 c may transmit loadsfrom the lug cluster 1 into the tube 2. The saddle 5 a, 5 b, 5 c mayhave a contour that matches the tube 2 and may be placed on the tube 2at the desired location. A fiber may be wound over the first sidethrough the first side groove 6 a according to the filament path 20 a orover the first side through the first side groove 6 b according to afilament path 20 b. A fiber may be wound over the second side throughthe second side groove 9 a according to the filament path 20 a or overthe second side through the second side groove 9 b according to afilament path 20 b. The fiber is wound until there is sufficient volumeof fiber to support the desired loading. A tension may be applied to thefiber during the wrapping to achieve integrity of the joint withoutdeforming the tube 2. The wrapping fibers thus compress the tube 2against the floor member 13 of the saddle 5 a, 5 b, 5 c of the lugcluster 1. As such, the lugs can be mounted to the tube 2 withoutdiminishment of the integrity of the tube 2 structure. The tube 2 andlug cluster 1 may be consolidated using resin transfer molding (“RTM”).Generally, resin transfer molding (“RTM”) includes a process where amolding material having a first material composition (e.g., a resin, athermosetting material, a thermoplastic material, composite, and/or thelike) is heated and injected into a mold encasing at least a portion ofthe lug cluster 1 and the tube 2. The molding material infiltratesand/or encases the lug cluster 1 and hardens. Following RTM andhardening of the resin, the assembly of the tube 2 and lug cluster 1 maybe machined to remove excess material of the upper infill member 12 andto finalize features such as the lightening pockets and attachmentpoints.

As such, attention is directed to FIGS. 1-6 with particular emphasis onFIG. 6. A method 500 of manufacturing a lug cluster 1 is disclosed. Afirst side 3 a, 3 b, 3 c may be formed comprising a flange with a firstside groove 6 a or a first side groove 6 b (Step 501). A second side 4a, 4 b, 4 c may be formed comprising a flange with a second side groove9 a or a second side groove 9 b (Step 503). The first side 3 a, 3 b, 3 cand second side 4 a, 4 b, 4 c are joined together by a saddle 5 a, 5 b,5 c comprising a floor member 13 comprising a planar member shaped tofollow a contour of a composite tube (Step 505). The first side 3 a, 3b, 3 c, the second side 4 a, 4 b, 4 c, and/or the floor member 13 of thesaddle may comprise various materials, such as, for example, metal,composite, plastic, fibrous material, and/or any material having desiredproperties. A first filament is wrapped along a filament path 20 a or afilament path 20 b disposed along the first side groove 6 a or the firstside groove 6 b and/or the second side groove 9 a or the second sidegroove 9 b, whereby the lug cluster 1 is secured in compression againstthe composite tube 2 (Step 507). The composite tube and the lug clusterare consolidated, such as via resin transfer molding and hardened (Step509). Moreover, an upper infill member 12 is formed comprising a firstmaterial composition resting on the floor member 13 and positionedbetween the first side 3 a, 3 b, 3 c and the second side 4 a, 4 b, 4 c(Step 511). Finally, attachment points and/or lightening pockets aremachined (Step 513).

Benefits, other advantages, and solutions to problems have beendescribed herein with regard to specific embodiments. Furthermore, theconnecting lines shown in the various figures contained herein areintended to represent exemplary functional relationships and/or physicalcouplings between the various elements. It should be noted that manyalternative or additional functional relationships or physicalconnections may be present in a practical system. However, the benefits,advantages, solutions to problems, and any elements that may cause anybenefit, advantage, or solution to occur or become more pronounced arenot to be construed as critical, required, or essential features orelements of the inventions. The scope of the inventions is accordinglyto be limited by nothing other than the appended claims, in whichreference to an element in the singular is not intended to mean “one andonly one” unless explicitly so stated, but rather “one or more.”Moreover, where a phrase similar to “at least one of A, B, or C” is usedin the claims, it is intended that the phrase be interpreted to meanthat A alone may be present in an embodiment, B alone may be present inan embodiment, C alone may be present in an embodiment, or that anycombination of the elements A, B and C may be present in a singleembodiment; for example, A and B, A and C, B and C, or A and B and C.Different cross-hatching is used throughout the figures to denotedifferent parts but not necessarily to denote the same or differentmaterials.

Systems, methods and apparatus are provided herein. In the detaileddescription herein, references to “one embodiment,” “an embodiment,” “anexample embodiment,” etc., indicate that the embodiment described mayinclude a particular feature, structure, or characteristic, but everyembodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed. After reading the description, it will be apparent to oneskilled in the relevant art(s) how to implement the disclosure inalternative embodiments.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. 112(f), unless the element is expressly recitedusing the phrase “means for.” As used herein, the terms “comprises,”“comprising,” or any other variation thereof, are intended to cover anon-exclusive inclusion, such that a process, method, article, orapparatus that comprises a list of elements does not include only thoseelements but may include other elements not expressly listed or inherentto such process, method, article, or apparatus.

What is claimed is:
 1. A lug cluster comprising: a first side comprisinga flange comprising a first side groove receiving a fiber filamentaccording to a filament path; a second side comprising a flangecomprising a second side groove receiving the fiber filament accordingto the filament path; and a saddle comprising: a floor member comprisinga planar member formed to follow a contour of a composite tube; an upperinfill member resting on the floor member and positioned between thefirst side and the second side.
 2. The lug cluster according to claim 1,wherein the floor member comprises a tube contour edge comprising an arccorresponding to a partial circumference of the composite tube.
 3. Thelug cluster according to claim 1, wherein the first side groovecomprises an arcuate profile and wherein the second side groovecomprises an arcuate profile.
 4. The lug cluster according to claim 1,further comprising a shear feature configured to correspond to aconjugate shear feature of the composite tube.
 5. The lug clusteraccording to claim 1, wherein the first side further comprises a firstside attachment point comprising an aperture defined by the first side.6. The lug cluster according to claim 5, wherein the second side furthercomprises a second side attachment point comprising an aperture definedby the second side and aligned to have a coaxial center with the firstside attachment point.
 7. The lug cluster according to claim 1, whereinthe first side comprises a first side lightening pocket comprising anaperture defined by the first side, and wherein the second sidecomprises a second side lightening pocket comprising an aperture formedthrough and defined by the second side.
 8. A method of manufacturing alug cluster comprising: forming a first side comprising a flangecomprising a first side groove; forming a second side comprising aflange comprising a second side groove, joining the first side andsecond side together by a saddle comprising a floor member comprising aplanar member shaped to follow a contour of a composite tube; wrapping afirst filament along a filament path disposed along the first sidegroove and the second side groove, whereby the lug cluster is secured incompression against the composite tube; consolidating the composite tubeand the lug cluster by resin transfer molding; and forming an upperinfill member resting on the floor member and positioned between thefirst side and the second side.
 9. The method according to claim 8further comprising machining a first side attachment point comprising anaperture defined by the first side.
 10. The method according to claim 9,further comprising machining a second side attachment point comprisingan aperture defined by the second side.
 11. The method according toclaim 8, further comprising machining a first side lightening pocketcomprising an aperture defined by the first side.
 12. The methodaccording to claim 11, further comprising machining a second sidelightening pocket comprising an aperture defined by the second side. 13.The method according to claim 8, wherein the composite tube comprises alanding gear strut.
 14. The method according to claim 8, furthercomprising forming a tube contour edge on an edge of the floor membercomprising an circle section having a radius equal to the radius of thecomposite tube.
 15. The method according to claim 14, wherein thecomposite tube comprises a landing gear strut.
 16. A landing gear systemcomprising: a composite tube comprising at least one of: a filamentwound composite tube; a filament braided tube; and a composite tube oflaid up filament; a first lug cluster mounted to the composite tube; asecond lug cluster mounted to the composite tube, and wherein the firstlug cluster and the second lug cluster are oriented at an angle to oneanother.
 17. The landing gear system according to claim 16, wherein thefirst lug cluster comprises: a first side comprising a flange comprisinga first side groove receiving a fiber filament according to a filamentpath; a second side comprising a flange comprising a second side groovereceiving the fiber filament according to the filament path; and asaddle comprising: a floor member comprising a planar member formed tofollow a contour of the composite tube; an upper infill member restingon the floor member and positioned between the first side and the secondside.
 18. The landing gear system according to claim 17, wherein thesecond lug cluster comprises: a second lug first side comprising aflange comprising a first side groove receiving a fiber filamentaccording to a filament path; a second lug second side comprising aflange comprising a second side groove receiving the fiber filamentaccording to the filament path; and a second lug saddle comprising: afloor member comprising a planar member formed to follow the contour ofthe composite tube; an upper infill member resting on the floor memberand positioned between the first side and the second side.
 19. Thelanding gear system according to claim 18, wherein the composite tubecomprises a landing gear strut.
 20. The landing gear system according toclaim 17, wherein the floor member comprises a tube contour edgecomprising an arc corresponding to a partial circumference of thecomposite tube.